A number of padding devices to relieve impact forces are known. For example, walking, jogging, and running generate large forces which are transferred throughout the body to such stress-sensitive areas as the knee and hip joints, as well as the lower back, where they then must be absorbed by the body. However, the origin of impact is the feet, and although quite possibly not as stress-sensitive as the above identified regions, the pressures experienced by the feet are magnified by the impact forces being applied over a relatively small area, typically the ball and heel of the foot. Consequently, there have been numerous attempts to not only reduce the overall stress imposed upon the body, but to also reduce the level of discomfort often experienced by the feet, all by utilizing impact absorbing devices in footwear.
Foam cushions are commonly used in footwear and other articles of clothing for absorbing impact force and can either be built into the footwear or be separately insertable. The basic concept of utilizing extra foam cushioning is that some of the forces of impact will be dissipated or absorbed in compressing the foam cushion. When the force is removed, the foam cushion will theoretically expand, in essence reinitializing itself for repeated absorbtion of impact forces.
There are a wide variety of foams available which have different properties and characteristics. However, foams in general have numerous inherent deficiencies which adversely affect their performance as impact force absorbers. For instance, "soft" foams offer little or no protection and dissipate little if any of the energy transferred at impact since they are easily compressed, and in fact tend to bottom out (fully compress) when subjected to a large force. "Harder" foams, on the other hand, may dissipate more energy by having a higher resistance to compression, but such pads will tend to adversely affect the comfort experienced by the user since there will not be much "give" in the pad, resulting in the impact forces being transferred to the body.
Regardless of the type of foam used as an impact force absorber, there may also be problems with an undesirable increase in the weight, for example, of the shoe in which the pad is used. Moreover, the lateral stability offered by the footwear by use of the additional foam pad may deteriorate since the distance from the ground to the bottom of the foot will quite naturally increase, thereby increasing the possibility of a user injuring an ankle or knee. Furthermore, a natural inherent characteristic of most foams is that over a given number of cycles of compression and expansion, the resiliency will eventually be affected such that the foam will become fatigued and no longer absorb impact forces as effectively as a foam which has not experienced cyclic fatigue.
Because of these types of undesirable characteristics exhibited by foam materials, numerous alternatives for absorbing impact forces have been developed. Instead of using foams as the impact absorbing medium, gases such as air and various liquids have been incorporated into certain configurations to enhance the impact absorbtion and distribution characteristics provided, for example, by footwear padding devices. Some of these alternative methods and devices will be discussed in the following paragraphs.
U.S. Pat. No. 4,263,728 by Frecentese, issued Apr. 28, 1981, discloses a jogging shoe with an adjustable shock absorbing system. The shock absorbing system includes a plurality of inwardly compressible piston-like protrusions on the bottom of the sole which communicate with a single air chamber contained within the sole of the shoe. The air chamber is inflated to an initial pressure by means of a valve which accesses the air chamber from outside the sole of the shoe. In operation, as a person walks, jogs, or runs, the pistonlike protrusions on the bottom of the sole of the shoe individually compress as they contact the ground. This compression of the pistons compresses the air contained within the air chamber which results in the absorbtion and distribution of the impact forces. Although Frecentese discloses a shock absorbing system for footwear, the disclosure is restricted to using air in a single chamber as the shock absorbing medium. Moreover, the disclosure of Frecentese is restricted to a system which is constructed within the sole of the shoe. Consequently, if the shock absorbing system fails, presumably the entire shoe would have to be replaced.
U.S. Pat. No. 4,342,157 by Gilbert, issued Aug. 3, 1982, discloses a shock absorbing system made up of two independent cushions which are both filled with a liquid and a gas, the liquid occupying a majority of the volume of the cushion. These cushions are constructed within the sole of a shoe and are preferably placed in those portions of the shoe coinciding with the heel and ball areas of the foot. The apparent shock absorbing concept desired by Gilbert is simply providing compressible cushions to protect these areas of the foot, the cushions merely being a liquid/gas combination rather than a foam. Although disclosing the use of liquid/gas-filled cushions in footwear, there is no disclosure or suggestion of using any fluid communication between the chambers as a way to absorb and/or distribute impact forces. Furthermore, the disclosure requires that the cushions be constructed within the sole of the shoe. Consequently, if the cushions rupture, the entire shoe would presumably have to be replaced.
U.S. Pat. No. 4,217,705 by Donzis, issued Aug. 19, 1980, discloses a flexible, self-contained, fluid-filled support device for use in footwear. The support device is an insertable cushion which approximates the contour of a foot. The cushion is formed by sealing two plies of material on the periphery and then sealing numerous portions of the cushion interior of the periphery to form a plurality of interconnected chambers. Fluid communication between the chambers is limited to a path around the periphery and is further restricted when the cushion is flexed, which in essence pinches off the flow channels to effectively create a plurality of isolated chambers. Therefore, impact forces are absorbed by deformation of the cushion without utilizing a substantial transfer of fluid to lower pressure regions of the cushion to more effectively absorb and/or distribute impact forces. Moreover, there is no disclosure or suggestion that the individual chambers are capable of a self-pumping action to transfer fluid throughout the pad, instead requiring the application of a force thereon to transfer a limited amount of fluid to other regions of the pad.
U.S. Pat. No. 4,538,902 by Cole et al., issued Nov. 16, 1982, discloses a shock absorbing system having interconnected, fluid-filled chambers which are partially constructed within the sole of the shoe. Although a majority of the chambers are contained within the sole, a portion of each cushion extends beneath the sole and thus actually comes into contact with the ground. One embodiment suggests positioning one chamber to coincide with the heel and two chambers to coincide with the ball area of the foot, the heel chamber being fluidly communicable with the two ball area chambers. The shock absorbing function disclosed by Cole et al. begins with the heel impacting the heel chamber. This impact deforms the heel chamber and forces some of the fluid contained therein to flow into the two ball area chambers. When the ball area chambers strike the ground, these chambers deform and some of the fluid contained therein is forced to flow back into the heel chamber. Consequently, fluid is transferred from front to back to absorb and distribute the impact forces. Although disclosing an interconnected, multi-chambered, fluid-filled shock absorbing system, Cole et al. do not disclose or suggest that any of the chambers themselves exhibit a self-pumping action, instead requiring the application of a force to transfer fluid to the other chamber or chambers. Moreover, the disclosure is restricted to a system which is constructed within the sole of the shoe. Furthermore, Cole et al. do not disclose or suggest providing for improved lateral support by using chambers in the shoe which are positioned around the periphery of the foot or a portion thereof.
U.S. Pat. No. 4,458,430 by Peterson, issued Jul. 10, 1984, discloses a shock absorbing system constructed within the sole of a shoe consisting of two interconnected, fluid-filled chambers. The chambers are positioned under the heel and arch portions of the foot. Unlike the assembly disclosed in Cole et al. above, the chambers are totally contained within the sole of the shoe, i.e., the chambers do not bulge below the sole of the shoe. The impact absorbing function initiates when the heel strikes the rear chamber and the fluid contained therein is forced to flow into the other chamber, causing it to expand. The chambers, however, provide a certain resistance to expansion. This, coupled with the somewhat restricted connecting passageways, serves to absorb some of the impact forces. The process is reversed when the forward cushion experiences an applied force. Although Peterson discloses a multi-chambered, fluidly connected impact absorbing device, the disclosure of Peterson is restricted to a system which is constructed within the shoe. A further problem with the systems disclosed by both Peterson and Cole et al. is that they provide no impact absorption if both chambers are compressed simultaneously as presumably would happen when one jumps straight up and down. Moreover, Peterson does not disclose or suggest providing improved lateral support by placing chambers in the shoe around the periphery of the foot or a portion thereof. Furthermore, Peterson does not disclose or suggest that some of the chambers exhibit self-pumping characteristics, instead requiring the application of a force to a chamber to transfer fluid to the other chamber.
In summary, the above-discussed padding devices for footwear which use a fluid medium to absorb and/or distribute impact forces are inadequate in a number of respects. Initially, many of the references disclose devices which are built into the sole of the footwear. When any portion of the shock absorbing system malfunctions or wears out, the entire shoe presumably must be replaced. In addition, none of the references appear to disclose improving the lateral support of the shoe by positioning a chamber or chambers around the periphery of the foot or a portion thereof. Furthermore, all of the references which implement interconnected, multi-chambered shock absorbing systems require that a force be exerted on or near the chambers themselves to move fluid to lower pressure regions. Therefore, if forces are not alternatively applied to each chamber in a precisely timed manner, they will not function effectively.
It would be advantageous to have a padding device which overcomes the deficiencies of known devices, namely by providing a padding device which uses fluidly communicable chambers to effectively and efficiently absorb and distribute impact forces, and which is self reinitializing for subsequent use. It would also be advantageous to provide a device which improves the lateral support of footwear for applications where such a feature would be appropriate.